This project is designed to investigate the prenatal maturation of the human lung surfactant system in both normal and high risk pregnancies by comparing compositional changes of purified surfactant. Amniotic fluid surfactant, purified by density gradient centrifugation, obtained at term and at various times during gestation from normal pregnancies will be analyzed to determine in detail the nature of changes in phospholipids, neutral lipids and protein components, thereby defining the normal developmental pattern of fetal lung surfactant. Similar studies will be carried out on surfactant from high risk pregnancies to determine if the composition of surfactant differs from that of normal pregnancies. Of particular interest are pregnancies complicated by diabetes which leads to a high incidence of RDS, and those complications such as pre-eclampsia and chronic hypertension which may lead to an early attainment of a "false positive" lecithin to sphingomyelin (L/S) ratio.